Tank retainer



FIG. 1 is a front perspective illustration embodying our new design;

FIG. 2 is a front plan view;

FIG. 3 is a side plan view;

FIG. 4 is a rear plan view;

FIG. 5 is a top plan view; and,

FIG. 6 is a bottom plan view. 

The ornamental design for a tank retainer, as shown. 